It's something called "cup grease" which was supposed to lubricate the upper bushing of the distributor. I doubt if it's even sold anymore. It's too thick to be pumped through a pneumatic grease gun- - - -we got a drum of it by mistake at a service station where I worked in the early 1960's and it clogged up the whole lube system. If you clean it out, try using disc brake wheel bearing grease as a substitute. Fill the cup about halfway, and screw it onto the fitting, after cleaning out the passageway all the way to the distributor shaft with a small drill bit. Once the passage is filled all the way to the shaft, top it off and tighten the fitting until it's snug. Give the cap about 1/4 to 1/2 turn at every oil change.
Jerry
